1. Field of the Invention
This invention relates to a whey protein gel comprising whey protein dissolved or dispersed in water or a buffer solution and poly-L-lysine or its salt, and a process for producing the gel. The whey protein gel may be used as a whey protein-containing jelly and a jelly-like beverage, and further may be preferably used as a binder, a stabilizer or a bulking filler for meats or may be used for preparing sausage, hamburger, meats for steak, "Kamaboko" (a Japanese term; a kind of boiled fish paste), etc.
2. Description of the Related Art
Whey protein is obtained as a byproduct in the production of cheese and casein, and it has been known to be a protein having a high nutritive value. However, a method of effectively utilizing the whey protein has not yet been established. Further, it has been known that when whey protein is heated and then cooled, it gels in the form of a denatured gel, like other proteins. However, such a denatured gel obtained by heating the whey protein has a defect that it is unstable to heat, for example, when it is heated to 100.degree. C. or higher, the gel is destroyed.
As an attempt to obtain a thermostable whey protein gel, urea or guanidine hydrochloride has been added to whey protein. However, it is impossible to use urea and guanidine hydrochloride for foods; hence whey protein gel produced in the presence of urea or guanidine hydrochloride are stable to heat, but have a serious defect in that they cannot be utilized for foods.
The present inventors have made extensive research in obtaining a whey protein gel having high safety as foods and also a high thermostability, unlike conventional whey protein gels made by using urea or guanidine hydrochloride. As a result, we have found that when poly-L-lysine is added to a whey protein solution or dispersion dissolved or dispersed in water or a buffer solution, it is possible to prepare a transparent and thermostable gel at room temperature, unlike gels obtained by thermally denaturing proteins. Further, we have found that when the gel obtained by adding poly-L-lysine to whey protein is heated, the resulting gel is firmer and/or more rigid. Thus it is possible to apply the process of the present invention together with known gelation process by heating whey protein. Thus, the present invention has been completed.